U.S. Pat. No. 6,160,764 discloses an electric trolling motor for propelling a boat comprising an electric propulsion motor having a substantially cylindrical motor housing and an electric trolling motor end cap for mounting and protecting a transducer therein, the end cap comprising a body portion having a recess integrally formed therein for receiving a transducer in the recess and a transducer removably mounted in the recess, a bore formed in the end cap creating a passageway extending from the exterior of the end cap to the interior of the recess, and a releasable air pressure seal for obturating the passageway and retaining the transducer in the recess when the passageway is obturated, and releasing the air pressure seal when the passageway is opened; also, a novel end cap for electric trolling motors.
U.S. Pat. No. 6,652,331, which is incorporated herein by reference, discloses a trolling motor having an integral sonar transducer including: a submerged motor housing; an electric motor housed in the housing; a sonar transducer housed in the housing; a motor controller having a pulse width modulated output and a shielded electrical cable connecting the sonar transducer to a sonar device. Noise from all sources (i.e., electrical noise from ground loops, radio frequency interference, and magnetic interference) is suppressed in the output signal of the transducer through a number of techniques. The electrical cable includes an outer shield connected to the chassis ground of the trolling motor; an inner shield connected to the circuit ground of the sonar device; and a pair of signal carrying conductors comprising a twisted pair. In addition, the resonant frequency of the transducer is selected such that it is not a harmonic of the operating frequency of the pulse width modulated output of the motor controller.
U.S. Pat. No. 6,661,742 discloses a trolling motor system including a lower propulsion unit and a transducer assembly. The lower propulsion unit has an external cavity extending into the lower propulsion unit. The transducer assembly includes a sonar transducer and a mount coupled to the sonar transducer. The mount releasably secures the sonar transducer within the cavity. In one exemplary embodiment, the mount includes at least one fastener releasably coupling the mount to the lower propulsion unit. In one exemplary embodiment, the mount releasably secures the sonar transducer within the lower propulsion unit proximate a rear end of the lower propulsion unit.